Modern ink jet printers may produce photographic-quality images. An inkjet printer includes a number of orifices or nozzles spatially positioned in a printer cartridge. Ink is heated when an electrical pulse energizes a resistive element forming a thermal resistor. The ink resting above the thermal resistor is ejected through the orifice towards a printing medium, such as an underlying sheet of paper as a result of the applied electrical pulse.
The thermal resistor is typically formed as a thin film resistive material on a semiconductor substrate as part of a semiconductor chip, for example. Several thin film layers may be formed on the semiconductor chip, including a dielectric layer carried by the substrate, a resistive layer forming the thermal resistor, and an electrode layer that defines electrodes coupled to the resistive layer to which the pulse is applied to heat the thermal resistor and vaporize the ink.
A first phase of making a print head, which may include the components described above, may follow standard semiconductor processing techniques to form circuitry for controlling the inkjet print head. The control circuitry may be formed on a front side of a silicon wafer, for example, a silicon wafer having a <100>crystalline orientation and 675-725 micron thickness.
Once the circuit formation processing steps are completed, two additional phases for making a print head are typically followed. These phases are generally classified as micro electro-mechanical systems (MEMS) processing steps. One of these MEMS phases may include forming three-dimensional structures that function as inkjet chambers, which may be formed on the same side of the wafer as the control circuitry. The thermal resistor or heater, which is described above, may be carried by a floor of each inkjet chamber. Each inkjet chamber acts as a small room into which ink flows. A roof of each inkjet chamber typically includes an opening, which may be referred to as an orifice, bore, or nozzle plate, for example.
The other MEMS processing phase may include forming through-wafer ink channels to allow ink to flow from a reservoir or supply at the backside of the wafer to each inkjet chamber. This MEMS phase may be relatively expensive. For example, one method of forming the through-wafer ink channels is deep reactive ion etching (DRIE) of silicon, which uses relatively expensive equipment and has a very low throughput. Another common method is laser cutting, which also uses relatively expensive equipment and has a very low throughput.
One technique for forming a through-wafer ink channel includes forming an ink feed slot in a substrate using a saw. More particularly, U.S. Pat. No. 7,966,728 to Buswell discloses using a circular cutting disk or saw positioned above a first surface of a substrate to cut a desired depth of the substrate.